The present invention relates to an automobile engine cooling system, and more particularly, to a cooling system having two thermostats to improve cooling efficiency.
An automobile engine in general is equipped with a cooling system, which is designed to radiate the heat produced as a result of burning in the combustion chamber. Engine cooling systems are commonly classified into three different types: an air cooling type wherein cylinder is cooled by exposing to the air, a water cooling type wherein cylinder is cooled by circulating water around the cylinder block, and a mixed type wherein cylinder is cooled by using both types.
In conventional water-type engine cooling systems, most of the cooling water is supplied to the cylinder block at the time of the initial engine start-up and thus raises a number of problems. First, the cylinder rapidly cools down beyond the desired level, which leads to deformation of the bore of the cylinder. In particular, the bore of the first cylinder becomes easily deformed because cooling water introduced from the outside first flows into the first cylinder of the cylinder block. Another problem is that the deformation of the cylinder bore increases the friction between the bore and the piston and as a result quickly increases the temperature of oil and the internal surface of the cylinder block thereby deteriorating fuel consumption. Also, the cooling water is supplied to the cylinder head via the cylinder block, and thus a vast amount of cooling water is required due to an increase in resistance against cooling water throughout the water passage of the engine.
The present invention provides an engine cooling system that includes two thermostats to delay the flow of cooling water in the cylinder block. Cooling water is supplied to the cylinder block and the cylinder head through two separate lines, respectively. Further, when cooling water rises beyond a predetermined temperature, cooling water confined in the cylinder block becomes mixed with cooling water that is in a process of circulation around the cylinder head without circulating through the radiator, and then guided to circulate through the radiator.
In preferred embodiments of the invention, cooling water is supplied into the cylinder head and cylinder block by a water pump and the circulation of the cooling water is selectively directed to the water pump or a radiator. The cooling water is respectively supplied into a cylinder head and cylinder block via two separate lines and the system is equipped with two thermostats. A main thermostat is disposed in the outlet line of the cylinder head. An auxiliary thermostat is disposed in the outlet line of the cylinder block and connected to the outlet line of the cylinder head. The main thermostat operates at a lower temperature than that of auxiliary thermostat and the auxiliary thermostat supplies a part of the cooling water to the outlet line of the cylinder block in a closed state.
In a preferred embodiment of the present invention, the cooling water supplied through inlet lines of the cylinder head and cylinder block accounts for about 55% and about 45% of the total cooling water, respectively. Preferably, the main thermostat connects the water passage to the water pump at a temperature below about 82xc2x0 C. while connects it to the radiator at a temperature above about 82xc2x0 C. The auxiliary thermostat is preferably closed at a temperature below about 95xc2x0 C. but is open at a temperature above about 95xc2x0 C. While closed, the auxiliary thermostat enables flow of about 5% of the cooling water in the cylinder block to the main thermostat.
The main thermostat and the auxiliary thermostat are both disposed within the water passage for cooling water circulated inside the cylinder block and cylinder head as well as within the assembly of the water passage jacket that connects the cooling water to the radiator. The overall length of the water jacket in the above cylinder block is preferably equivalent to about 50% to 60% of that of piston stroke. The water pump is disposed in counter location relative to the assembly of the water passage thereby allowing the cooling water to flow into the cylinder block and the cylinder head.